Motor pump unit



Aug. 6, 1968 G. GREBEL ET AL 3,395,644

MOTOR PUMP UNIT Filed June 16, 1966 1 j 27 I ji 2a \/z4 I 9 a 7 ,"22 I HI2 INVENTORS 0 GRANT Fig.3.

ROGER J. KINNAVY United States Patent 3,395,644 MOTOR PUMP UNIT GrantGrebe], St. Joseph, and Roger J. Kinnavy, Benton Harbor, Mich.,assignors to Sta-Rite Products, Inc., Delavan, Wis., a corporation ofWisconsin Filed June 16, 1966, Ser. No. 558,013 Claims. (Cl. 103-87)ABSTRACT OF THE DISCLOSURE The invention relates to a motor-pump unitfor use in a'closed water pumping system which prevents the buildup ofmagnetite on the liner and other elements in the motor chamber. The unitincludes a dynamic face-type seal for the rotor shaft in which the shaftis provided with a shoulder adapted to engage, and seal against, theinner end of the bearing during conditions of outward thrust. Inaddition, the impeller, which is carried by the shaft, is provided witha sealing ring and under conditions of inward thrust, the ring isadapted to bear against the outer end of the bearing to provide a seal.

Under non-operating, no-thrust conditions, the ends of the hearing arespaced from the respective sealing members so that small amounts ofwater can pass through the seal faces and along the shaft to make up forminute quantities of water lost from the rotor chamber due to leakagethrough static seals.

In addition, a check valve is provided between the rotor chamber and thepumping chamber and under conditions of continuous operation of thepump, the check valve permits the flow of small amounts of water fromthe pumping chamber to the rotor chamber to make up for leakage.

This invention relates to a motor-pump unit and more particularly to amotor-pump unit to be used in a hot water pumping system.

Two types of motor-pump units are commonly used in closed pumpingsystems. One type is generally referred to as a dry-motor type in whichthe motor is protected from the liquid being pumped by a mechanical sealor the like. The second type is a wet-motor type in which the stator androtor of the motor are separated by a thin metal liner or shell and theliquid being pumped is circulated within the rotor chamber to lubricatethe bearings as well as to cool the bearings and the motor itself.

In a hot water heating system, the water is normally circulated througha ferrous boiler and sometimes through ferrous pipes, hence the watercontains iron oxide corrosion products. When the system is closed to theatmosphere, the amount of oxygen in the system is limited, and the ironoxide is primarily in the form of Fe O or magnetite, which is attractedby magnetic fields. In the conventional wet-type, motor-pump unit, themagnetic particles of magnetite enter the rotor chamber and areattracted to the magnetic field of the motor, thereby depositing on theliner, rotor and hearings in the rotor chamber. The buildup of themagnetite particles on the liner and on other elements in the rotorchamber can eventually bind and stall the motor.

In the past, attempts have been made to prevent the buildup of magnetiteon the elements within the rotor chamber, but these attempts have notmet with great success. It has been proposed to employ a porous plugwithin an opening connecting the rotor chamber and the pumping chamber,with the purpose of the plug being to restrict the flow of magneticparticles into the rotor chamber. However, the porous plug permits theflow of liquid in both directions and due to temperature variations ofthe water within the rotor chamber, water flow will normally occurbetween the rotor chamber and the pump- 3,395,644 Patented Aug. 6, 1968"ice ing chamber. The magnetite particles are very small in size and atleast a portion of the magnetite particles will pass through a porousplug type of filter with the result that the magnetite will continue tobuild up on the liner. As an added problem, larger foreign particleswill tend to accumulate on the surface of the porous plug and mayeventually clog the plug.

The present invention is directed to a wet-type of motor for use in aclosed water pumping system which prevents the buildup of magnetite onthe liner and other elements in the rotor chamber.

According to the invention, the rotor chamber water is separated fromthe pumpage during the operation by a dynamic face-type fluid seal.Thus, the only magnetite in the rotor chamber is that contained in thewater used for the initial filling of the rotor chamber and this amountof magnetite is very small. When the pump is operating, the rotorchamber is sealed. When the pump is not in operation, small amounts of.water can pass through the seal faces to make up for minute quantitiesof water lost from the rotor chamber due to leakage through staticseals. This amount of leakage is extremely small so that the buildup ofmagnetite in the liner or other elements of the rotor chamber isnegligible. In systems where the pump is operated continuously, thecharacteristics of the invention are attained by use of a check valve.An opening is provided between the rotor chamber and pumping chamber anda check valve is located within the opening. The check valve permits theflow of water from the pumping chamber to the rotor chamber, butprevents the flow of water in the opposite direction. The rotor chamberis filled with Water which is in a substantially static condition, andthere is no appreciable flow of water through the check valve duringordinary operating conditions. As the only flow of water through thecheck valve into the rotor chamber will be the replacement of minutequantities of Water lost from the rotor chamber due to leakage throughthe seals, there will be no appreciable buildup of magnetite on theliner or other elements in the rotor chamber. Moreover, the check valvewill permit relatively large particles to pass therethrough and does notattempt to filter out foreign materials, with the result that there willbe no clogging of the check valve after extended periods of use, as inthe case of a porous plug or other filter element.

As the present invention reduces the buildup of magnetic particleswithin the rotor chamber, it substantially reduces the maintenance for awet-type of motor unit which is to be employed in a hot Water heatingsystem.

Other objects and advantages will appear in the course of the followingdescription.

The drawings illustrate the best mode presently contemplated of carryingout the invention.

In the drawings:

FIG. 1 is a longitudinal section of the motor-pump unit of theinvention;

FIG. 2 is a view taken along line 2-2 of FIG. 1; and

FIG. 3 is an enlarged longitudinal section showing the motor shaftbearing, shaft seal and check valve in a .nonoperating condition of thepump.

The drawings illustrate a wet-type, motor-pump unit adapted to be usedin a hot water heating system and the unit comprises a pump 1 whichisdriven by a motor 2.

The pump 1 includes an outer casing 3 which defines a pumping chamber 4.Water is introduced into the pumping chamber through an inlet passage 5and opening 6 which connects passage 5 and the pumping chamber 4. Casing3 is provided with a flange 7 bordering inlet passage 5, and flange 7 isbolted to a flanged fitting 8 having a threaded opening which receivesan inlet pipe 9.

The casing 3 also defines a volute or discharge passage which extendsfrom the pumping chamber 4, and the casing is provided with a flange 11bordering the outlet of passage 10. Flange 11 is connected to a flangedfitting 12 by a series of bolts and a discharge pipe 13 is threadedwithin the fitting 12.

Located within the pumping chamber 4 is a conventional impeller 14 whichis driven by the motor shaft 15 attached to rotor 16. As best shown inFIG. 3, the rotor shaft 15 is provided with a shoulder 17 which bearsagainst the upper end of bearing 18. The lower end of the bearing 18rides against a ring 19 which is bonded to a rubber or resilient ring 20fitted within a recess 21 in the upper end of the impeller 14. Duringoperation of the motor, there is a downward thrust produced by theimpeller which brings the shoulder 17 into bearing engagement with theupper end of bearing 18 to provide a mechanical shaft seal. If at anytime the thrust is upward, the ring 19 bears against the lower end ofthe bearing 18 to similarly provide a shaft seal. If the pump is notoperating, the bearing 18 will normally be spaced from both shoulder 17and ring 19 and this spacing permits the liquid under line pressure topass along shaft 15 to the rotor chamber, as will be describedsubsequently.

The bearing 18 is mounted within a recess formed in an adapter plate 22which is sealed with respect to the pump casing 3 by an annular seal 23.

The motor 2 includes an outer casing 24 connected to the pump casing 3by a series of bolts 25. The upper end of the motor casing 24 is formedwith a downwardly extending annular ring 26 which serves as a mount orsupport for a bearing 27 that journals the upper end of the motor shaft15.

Located centrally of the upper end of motor casing 24 is a vent holewhich is enclosed by a threaded plug 28.

The stator 29 of motor 2 is separated from the rotor 16 by a thin metalliner or shell 30. The upper end of the liner 30 is sealed to the motorcasing 24 by the annular seal 31, while the lower end of the liner 30 issealed to the adapter plate 22 by seal 32.

With a wet-type of motor, the pumped liquid is circulated in the rotorchamber 33 and serves not only to lubricate the bearings but also tocool the bearings and the motor. In a hot water heating system where thesupply of oxygen is limited the ferrous products of corrosion are notcompletely oxidized and exist primarily as Fe O or magnetite which ismagnetic in character. Thus, the magnetic particles of magnetite will beattracted to the magnetic field of the conventional wet-type motor andwill be deposited on the liner as well as on other elements within therotor chamber 33, and this accumulation of magnetite may bind and stallthe motor. As the motor used in a conventional motor-pump unit for a hotwater heating system generally has a low starting torque, the motor doesnot have the capability of spinning free from the binding accumulationof magnetite.

The present invention overcomes this problem which occurs in aconventional wet-type motor-pump unit, by separating the rotor chamberwater from the pumpage by use of a dynamic seal. During operation of thepump, the thrust of the impeller closes the gap between the shaftshoulder 17 and the corresponding face of the bearing 18 to provide aseal and prevent the pumpage from entering the rotor chamber. When thepump is not operating, the ends of bearing 18 are spaced from theshoulder 17 and ring 19, respectively, to permit the pumpage under linepressure to pass along shaft 15 to rotor chamber 33.

In addition to the dynamic shaft seal, a check valve 34 is located in anopening 35 in the adapter plate 22. Check valve 34 permits the flow ofliquid from the pumping chamber 4 into the rotor chamber 33 but preventsthe fiow of liquid in the opposite direction. The check valve 34, asshown in the drawings, is a flap-type formed of a resilient material,such as rubber, and having a tubular body 36 secured with opening 35.The upper end of the body36 terminates in a crimped end or flap 37 43 pwhich, under balanced pressure conditions, provides a closure. It iscontemplated that other types of conventional check valves can beemployed to control the flow of liquid through the opening 35.

While the drawings illustrate the use of a single check valve 34 tocontrol the flow of liquid between the pumping chamber 4 and the rotorchamber 33, it is contemplated that a series of check valves can beemployed if desired. Moreover, check valve 34 is shown as communicatingwith the discharge passage 10 of the pump. While this is a preferredconstruction, it is also possible to provide communication between therotor chamber 33 and the inlet passage 5 or suction side of the pump, asthere is sufiicient pressure both on the inlet and discharge sides ofthe pump to force thewater or other liquid through the check valve 34 tothe rotor chamber 33.

At the start of operation, the rotor chamber 33 is filled with water byinitially removing the vent plug 28 and starting the pump. Water will beforced from the discharge passage 10 through the check valve 34 into therotor chamber 33 to fill the same and exhaust the air from the rotorchamber. When the rotor chamber has been filled with water, the ventplug 28 is replaced.

During operation of the pump, there will be no appreciable circulationof water between the pumping chamber 4 and the rotor chamber 33 due tothe fact that a dynamic seal is formed between shaft face 17 and face ofbearing 18 and the check valve 34 permits flow of water only in onedirection. This prevents the water being pumped, which containsparticles of magnetite, from entering the rotor chamber and thereforeminimizes the accumulation of magnetite on the rotor elements. If aminute amount of water should leak from the rotor chamber through thevent plug 28 or shaft seal, this water is replaced by water being forcedthrough the check valve into the rotor chamber. However, under normalconditions, the amount of water lost by leakage is of a minute quantity,so that only a very small amount of magnetite will be brought into therotor chamber with the replacement water and will not cause anappreciable buildup of the liner 30 or other parts of the rotor.

The use of the valve 34 has distinct advantages over filters or porousplugs in that the check valve prevents the circulation of water betweenthe rotor chamber and pumping chamber so that no appreciable quantitiesof magnetite will flow into the rotor chamber. However, the check valve34 does permit the flow of small quantities of water into the rotorchamber to make up for water lost through leakage, so that the rotorchamber will be filled with water at all times. Moreover, as the checkvalve will permit particles of substantial size to pass therethrough,there is no danger of the check valve being clogged due to anaccumulation of particles or foreign material. Thus, the inventionenables the motor-pump unit to be operated for extended periods undertroublefree conditions with a minimum of maintenance.

As previously mentioned, during operation of the pump, shoulder 17 willbe in bearing engagement with the upper end of the bearing 18 to providea mechanical shaft seal, and if at any time the thrust is upward, thering 19 will bear against the lower end of bearing 18 to similarlyprovide a mechanical shaft seal. When the pump is not operating, thereis a sufficient space between the ends of bearing 18 and shoulder 17 andring 19 to permit water under line pressure to pass along shaft 15 torotor chamber 33. Thus, the bearing not only journals the shaft, but theends of the bearing act to provide mechanical seals, and undernon-operating conditions, the spacing is such that water can flow alongthe shaft, incooperation with the flow through check valve 34, to rotorchamber 33.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

We claim:

1. In a wet-type motor-pump assembly to be used in a closed pumpingsystem, a motor unit having a housing defining a rotor chamber and astator chamber and having means for sealing the rotor chamber from thestator chamber, said motor unit including a rotor and a rotatable shaftconnected to the rotor and extending outwardly of said rotor chamber, acasing defining a pump ing chamber and having an opening to receive saidshaft, an impeller located within the pumping chamber and secured to theshaft and disposed to rotate with the shaft, a bearing mounted in thecasing and disposed to journal said shaft for rotation, said bearinghaving a generally fiat outer end facing said impeller and having agenerally flat inner end facing said motor unit, a first abutment on theshaft and having a bearing surface facing the inner end of the bearing,and a second abutment on the shaft and having a bearing surface facingthe outer end of said bearing, the bearing having an axial length suchthat the ends of said bearing are spaced from the corresponding bearingsurfaces when the pump is not operating to permit the pumpage to flowunder line pressure along the shaft to the rotor chamber, duringoperation of the pump one of said ends being in engagement with thecorresponding bearing surface to provide a dynamic shaft seal andprevent the flow of pumpage to the rotor chamber.

2. The motor-pump assembly of claim 1, and including conduit meansproviding communication between the rotor chamber and the pumpingchamber, and check valve means disposed within said conduit means forpermitting the flow of pumpage from the pumping chamber to the rotorchamber but preventing flow in the opposite direction.

3. The motor-pump assembly of claim 2 in which said conduit meanscommunicates with the discharge side of the pumping chamber.

4. The motor-pump assembly of claim 1, in which said check valve meansis a resilient member having an end facing said rotor chamber whichunder balanced pressure conditions is normally biased closed.

5. In a motor-pump assembly, a casing defining a rotor chamber and apumping chamber and having a wall separating said rotor chamber fromsaid pumping chamber, a motor unit disposed within the casing andincluding a rotor disposed within the rotor chamber and a shaft memberconnected to the rotor and extending through an opening in said wall, abearing disposed within said opening for journalling said shaft memberfor rotation, an impeller member secured to said shaft member anddisposed within said pumping chamber, a first abutment on said shaftmember and having a bearing surface facing the inner end of saidbearing, a second abutment on one of said members and having a bearingsurface facing the outer end of said bearing, said bearing having anaxial length less than the distance between said first and secondabutments so that the ends of said bearing are spaced from thecorresponding bearing surfaces when the pump is not operating to permitliquid to flow under line pressure from said pumping chamber along theshaft member to the rotor chamber, one of said ends of the bearing beingin engagement with the corresponding bearing surface when the pump isoperating to provide a dynamic shaft seal and prevent the flow of liquidfrom the pumping chamber to the rotor chamber, conduit means disposedWithin the wall and providing communication between the rotor chamberand said pumping chamber, and check valve means located within saidconduit means for permitting flow of liquid from the pumping chamber tothe rotor chamber but preventing flow of said liquid in the oppositedirection.

References Cited UNITED STATES PATENTS 1,198,558 9/1916 Lawaczeck 103872,713,311 7/1955 White 10387 3,026,808 3/ 1962 Immouilli 103-87 3,138,106 6/ 1964 Lebkuchner 10387 3,163,116 12/1964 McCourty et al. 103-873,256,829 6/ 1966' Schneider 103-103 HENRY F. RADUAZO, Primary Examiner.

